Lifetime Prediction of High Tenacity Polyester Yarns for Hydrolytic Degradation Used for Soil Reinforcement
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ISSN 1229-9197 (print version) ISSN 1875-0052 (electronic version)
Lifetime Prediction of High Tenacity Polyester Yarns for Hydrolytic Degradation Used for Soil Reinforcement Hang-Won Cho1,2, Hyun-Jin Koo2*, Hongdoo Kim1, and Kap-Jin Kim1* 1
Department of Advanced Materials Engineering for Information and Electronics, Kyung Hee University, Yongin 17104, Korea 2 FITI Testing & Research Institute, Seoul 07791, Korea (Received June 14, 2019; Revised October 3, 2019; Accepted December 12, 2019) Abstract: The long-term strength is considered the various degradation mechanisms in the design of the reinforced soil structure so that ISO TR 20432 provides guidelines for the determination of the long-term strength of geosynthetics for soil reinforcement. Geosynthetics using polyester and polyamide are susceptible to hydrolytic degradation due to ester and amide group by condensation polymerization. In this study, the accelerated hydrolysis test was carried out to predict service lifetimes of polyester filament yarns which are widely used in geosynthetics for soil reinforcement. Two types of filament yarns with different carboxyl end groups (CEG) were immersed in distilled water at elevated temperature at 80, 90 and 95 oC up to 112 days for shortening the test times. The reduction in tensile strengths was evaluated as the rate of hydrolytic degradation along the time at each temperature. The failure times were estimated to reach 50, 60, 70, 80, 90 % of retained tensile strengths by linear regression using time as an independent variable and retained strength as a response variable. The service lifetimes of polyester filament yarns were predicted at service temperature using Arrhenius relation of failure times and temperatures. The service lifetimes of both polyester yarns are exceeding 100 years up to 80 % of retained strength at 20 oC of service temperature. This can provide guidance to designers and manufacturers of geosynthetics in calculating the specific reduction factor of hydrolytic degradation at 100 years of design lifetime. Keywords: Hydrolysis, Hydrolytic degradation, Long-term performance, Durability, Lifetime prediction, Arrhenius Relation, Accelerated test
polymer chain backbone is broken, leading directly to a loss of mechanical properties. In case of goesynthetics used for soil reinforcement, the polymers inside of geosynthetics can be exposed to chemical attack easily when the coated materials are damaged during the installation. Chemical degradation of polymers occurs by a variety of processes including oxidation and hydrolysis, depending on the type of polymer and on the acidity or alkalinity of the soil. ISO TS 13434 [2] provides guidance on the primary degradation modes for a wide range of polymers used within the geosynthetics. These degradation mechanisms are further influenced by temperature and moisture uptake for some polymers. Especially polyester is susceptible to hydrolysis in aqueous solutions or humid soil at all values of pH (internal hydrolysis) [2]. BS EN 12447 [3] is an index test method
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